What is the recommended management approach for a term pregnancy at the 98th percentile for size?

Management of a Term Pregnancy at 98th Percentile for Size

For a term pregnancy with suspected fetal macrosomia at the 98th percentile for size, expectant management with planned vaginal delivery is recommended unless the estimated fetal weight exceeds 5,000g in non-diabetic mothers. 1, 2

Definition and Risk Assessment

• Fetal macrosomia is typically defined as birth weight greater than 4,000g (8lb, 13oz), which complicates more than 10% of pregnancies in the United States 3
• Key maternal risk factors include obesity, excessive pregnancy weight gain, previous delivery of a macrosomic infant, diabetes mellitus, and post-term pregnancy 2, 4
• Accurate prediction of macrosomia is challenging, with both clinical examination and ultrasound estimates having significant margins of error 1

Recommended Management Approach

Antepartum Care

• Expectant management is the preferred approach for suspected fetal macrosomia at term 1, 3
• Early induction of labor is not recommended for suspected macrosomia as:
  • It at least doubles the risk of cesarean delivery without reducing shoulder dystocia risk 1
  • There is insufficient evidence that early induction improves maternal or neonatal outcomes 2
• Regular antenatal surveillance should continue with standard term pregnancy protocols 1

Labor and Delivery Planning

• Vaginal delivery remains appropriate for estimated fetal weights up to 5,000g in non-diabetic women 1, 2
• Consider cesarean delivery when:
  • Estimated fetal weight exceeds 5,000g in non-diabetic women 1
  • There is prolonged second stage of labor or arrest of descent 1
  • There are additional risk factors such as maternal diabetes 2

Intrapartum Management

• Close monitoring during labor is essential to detect signs of fetopelvic disproportion 3
• If labor fails to progress as expected, reassess the clinical situation considering the best estimate of fetal weight 3
• Avoid midpelvic operative vaginal delivery (forceps or vacuum) in cases of suspected macrosomia 1
• If cesarean delivery becomes necessary, ensure the incision is adequately sized to prevent difficult abdominal delivery 1

Potential Complications

• Maternal risks include:

  • Increased likelihood of cesarean delivery 2
  • Higher rates of postpartum hemorrhage 2
  • Increased risk of vaginal lacerations 2

• Fetal/neonatal risks include:

  • Shoulder dystocia (significantly increased when birth weight exceeds 4,500g) 1
  • Birth trauma, including clavicular fracture and brachial plexus injury (10-fold and 18-21 fold increased risk respectively with birth weight >4,500g) 1
  • Lower Apgar scores 2
  • Long-term risk of childhood obesity 2

Common Pitfalls to Avoid

• Relying too heavily on estimated fetal weight for management decisions, as both clinical and ultrasound estimates are prone to error 1, 3
• Performing unnecessary cesarean deliveries based solely on suspected macrosomia 1, 2
• Early induction of labor to limit fetal growth, which may increase cesarean delivery rates due to failed inductions 3
• Using midpelvic operative vaginal delivery techniques when macrosomia is suspected 1

Key Practice Points

• The diagnosis of fetal macrosomia is imprecise; ultrasound biometry is no more accurate than clinical palpation 1
• Suspected fetal macrosomia alone is not an indication for labor induction 1, 2
• Vaginal delivery remains appropriate for estimated weights up to 5,000g in non-diabetic women 1, 2
• Cesarean delivery should be considered with arrest of descent in the second stage of labor when macrosomia is suspected 1